Touch detecting method and touch detecting device

ABSTRACT

A touch detecting method includes determining a kind of a detected indicator based on a first area on a touch surface, obtaining a plurality of second capacitances formed by emphasizing a peak in comparison with a plurality of first capacitances by processing the plurality of first capacitances by a first filter in a case where the determining determines that the detected indicator is a stylus, deriving coordinates indicating a position of the stylus on the touch surface based on a second area on the touch surface, and deriving coordinates indicating a position of a finger on the touch surface based on a third area on the touch surface.

BACKGROUND Technical Field

The present disclosure relates to a touch detecting method and a touchdetecting device.

Description of the Related Art

A capacitive type touch detecting device includes a touch sensor inwhich a plurality of X-electrodes each extending in a Y-direction and aplurality of Y-electrodes each extending in an X-direction are arrangedso as to intersect each other. The touch detecting device is configuredto repeat, for all of the Y-electrodes in order, processing of, forexample, inputting a predetermined signal to a Y-electrode andextracting this signal from each X-electrode in order. When an indicatorsuch as a finger, or a stylus approaches a touch surface, a capacitanceoccurs between the indicator and an X-electrode and a Y-electrodepresent in the vicinity of the indicator, and a part of a currentflowing in the X-electrode through the capacitance is absorbed in thedirection of the indicator. Thus, the amplitude of the signal extractedfrom the X-electrode is decreased. The touch detecting device isconfigured to detect a capacitance at each coordinate from a change inthe amplitude, and derive, as position coordinates of the indicator,coordinates indicating a center of gravity of a region in which thedetected capacitance is equal to or more than a threshold value.

U.S. Patent Publication No. 2011/0001708 (hereinafter, PatentDocument 1) discloses an example of a capacitive type touch detectingdevice. When the touch detecting device according to the present exampledetects a first touch, the touch detecting device first determines,using a first threshold value, which of the finger and the stylus istouching. Then, a detection mode as a function of a determination resultis entered which detection mode includes a mode in which a subsequenttouch is interpreted with a second threshold value lower than the firstthreshold value. With regard to this second threshold value, paragraph[0025] of Patent Document 1 describes using a threshold value lower thanthe first threshold value in a case where the stylus is touching. On theother hand, paragraph [0028] of Patent Document 1 describes using athreshold value lower than the first threshold value in a case whereconversely the finger is touching.

However, a technology described in the foregoing Patent Document 1 maynot be able to detect the finger and the stylus suitably. Detaileddescription will be made in the following.

First, supposing that the second threshold value lower than the firstthreshold value is used to detect the finger, a maximum value ofcapacitances in the case of the finger is a rather large value incomparison with the first threshold value, and therefore an areadetected with the second threshold value (region in which capacitancesexceed the second threshold value) is extensive. Then, a differencebetween coordinates indicating the center of gravity of the area and anoriginal position indicated by the stylus is increased, so that itbecomes difficult to detect the finger suitably.

Next, in the case of using the second threshold value lower than thefirst threshold value for the stylus, changes in capacitances due toapproaching or touching of the touch surface by the stylus are verysmall, and it is therefore difficult, in the first place, to detect theposition of the stylus accurately based on the threshold valuedetermination on the capacitances. Hence, it is difficult to detect thestylus suitably even when the second threshold value lower than thefirst threshold value is used.

BRIEF SUMMARY

It is accordingly one object of the present disclosure to provide atouch detecting method and a touch detecting device that can suitablydetect a finger and a stylus.

A touch detecting method according to the present disclosure is a touchdetecting method performed by a touch detecting device connected to atouch sensor constituting a touch surface. The touch detecting methodincludes determining a kind of a detected indicator based on a firstarea on the touch surface, the first area being an area in which each ofa plurality of first capacitances corresponding to a plurality ofcoordinates on the touch surface exceeds a first threshold value,obtaining a plurality of second capacitances formed by emphasizing apeak in comparison with the plurality of first capacitances byprocessing the plurality of first capacitances by a first filter in acase where the determining determines that the detected indicator is astylus, deriving coordinates indicating a position of the stylus on thetouch surface based on a second area on the touch surface, the secondarea being an area in which each of the plurality of second capacitancesexceeds a second threshold value larger than the first threshold value,and deriving coordinates indicating a position of a finger on the touchsurface based on a third area on the touch surface, the third area beingan area in which each of the plurality of first capacitances exceeds athird threshold value larger than the first threshold value, in a casewhere the determining determines that the detected indicator is thefinger.

A touch detecting device according to the present disclosure is a touchdetecting device connected to a touch sensor constituting a touchsurface. The touch detecting device includes an analog to digitalconverter which, in operation, generates a digital signal based on ananalog signal received from the touch sensor; and a touch detectingcircuit coupled to the analog to digital converter. The touch detectingcircuit, in operation, determines a kind of a detected indicator basedon a first area on the touch surface, the first area being an area inwhich each of a plurality of first capacitances corresponding to aplurality of coordinates on the touch surface exceeds a first thresholdvalue; obtains a plurality of second capacitances formed by emphasizinga peak in comparison with the plurality of first capacitances byprocessing the plurality of first capacitances by a first filter in acase where the detected indicator is determined to be a stylus; derivescoordinates indicating a position of the stylus on the touch surfacebased on a second area on the touch surface, the second area being anarea in which each of the plurality of second capacitances exceeds asecond threshold value larger than the first threshold value; andderives coordinates indicating a position of a finger on the touchsurface based on a third area on the touch surface, the third area beingan area in which each of the plurality of first capacitances exceeds athird threshold value larger than the first threshold value, in a casewhere the detected indicator is determined to be the finger.

According to the present disclosure, it is possible to detect a fingerand a stylus suitably.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic block diagram depicting functional blocks of atouch detecting device according to an embodiment of the presentdisclosure;

FIG. 2 is a flowchart depicting processing performed by a touchdetecting circuit;

FIG. 3A is a schematic diagram depicting a distribution of capacitancesin a case where a finger is present on a touch surface, and FIG. 3B is aschematic diagram depicting a distribution of capacitances in a casewhere a stylus is present on the touch surface;

FIG. 4 is a diagram depicting an example of a Gaussian filter used at S6in FIG. 2;

FIGS. 5A and 5B are each a diagram depicting an example of a high-passfilter used at S7 in FIG. 2;

FIG. 6A is a schematic diagram depicting capacitances obtained byprocessing the capacitances depicted in FIG. 3B by the Gaussian filterdepicted in FIG. 4, and FIG. 6B is a schematic diagram depictingcapacitances obtained by processing the capacitances depicted in FIG. 6Aby the high-pass filter depicted in FIG. 5A or FIG. 5B;

FIG. 7A is a diagram depicting a more concrete example of thecapacitances detected in the case where the finger is in contact withthe touch surface, and FIG. 7B is a three-dimensional (3D) contour mapdepicting a distribution of the capacitances depicted in FIG. 7A;

FIG. 8A is a diagram depicting a more concrete example of thecapacitances detected in the case where the stylus is in contact withthe touch surface, and FIG. 8B is a 3D contour map depicting adistribution of the capacitances depicted in FIG. 8A;

FIG. 9A is a diagram depicting capacitances obtained by processing thecapacitances depicted in FIG. 8A by the Gaussian filter of FIG. 4, andFIG. 9B is a 3D contour map depicting a distribution of the capacitancesdepicted in FIG. 9A;

FIG. 10A is a diagram depicting capacitances obtained by processing thecapacitances depicted in FIG. 9A by the high-pass filter of FIG. 5B, andFIG. 10B is a 3D contour map depicting a distribution of thecapacitances depicted in FIG. 10A.

DETAILED DESCRIPTION

An embodiment of the present disclosure will hereinafter be described indetail with reference to the accompanying drawings.

FIG. 1 is a schematic block diagram depicting functional blocks of atouch detecting device 1 according to the present embodiment. Asdepicted in the figure, the touch detecting device 1 includes a touchsensor 2, a touch sensor controller 10, a storage device 20, and a hostcentral processing unit (CPU). A touch detecting method according to thepresent embodiment is performed by the touch sensor controller 10 amongthese constituent elements.

The touch sensor 2 is a device for detecting touch operation by a fingerF or a stylus P. The touch sensor 2 is, for example, disposed on thedisplay surface of a display device not depicted. The display device isa device that displays text and images under control of the host CPU. Aliquid crystal display or an organic electroluminescence (EL) display,for example, can be suitably used as the display device. The uppersurface of the touch sensor 2 forms a flat surface and constitutes thetouch surface of the touch detecting device 1. It is to be noted thatthe present disclosure is not limited to the touch detecting device 1having the display function but is also applicable to touch detectingdevices not having the display function such as digitizers.

The touch sensor 2 is, specifically, a capacitive type touch sensor. Asdepicted in FIG. 1, the touch sensor 2 has a configuration in which aplurality of X-electrodes 2 x each extending in a Y-direction andarranged at equal intervals in an X-direction and a plurality ofY-electrodes 2 y each extending in the X-direction and arranged at equalintervals in the Y-direction are arranged so as to intersect each other.The X-electrodes 2 x and the Y-electrodes 2 y constitute sensorelectrodes of the touch sensor 2. The X-electrodes 2 x and theY-electrodes 2 y are each formed by a transparent conductive materialsuch as an indium tin oxide (ITO) transparent conductive film. A user ofthe touch detecting device 1 can therefore view the display surface ofthe display device through the touch surface. When the finger F or thestylus P comes into contact with the touch surface, a capacitance occursbetween the finger F and X-electrodes 2 x and Y-electrodes 2 y in thevicinity of the finger F. The touch sensor controller 10 is configuredto detect the position of the finger F or the stylus P on the touchsurface by using this change in capacitance. This will be describedlater again in more detail.

As depicted in FIG. 1, the touch sensor controller 10 includes anoscillator 11, multiplexers 12 and 13, an analog to digital (A/D)converter 14, and a touch detecting circuit 15.

The oscillator 11 is a circuit that oscillates a signal of apredetermined frequency. In addition, the multiplexer 12 is a circuitthat plays a role of selecting the plurality of X-electrodes 2 x one byone in order at predetermined time intervals and connecting theoscillator 11 to the selected X-electrodes 2 x. Due to an action of themultiplexer 12, a signal output by the oscillator 11 is supplied to eachof the plurality of X-electrodes 2 x in order. The signal supplied tothe X-electrode 2 x is supplied to each Y-electrode 2 y through anintersection position (i, j) of the X-electrode 2 x and each Y-electrode2 y. Here, i and j are respectively natural numbers indicating serialnumbers of the X-electrodes 2 x and the Y-electrodes 2 y. A combination(i, j) of i and j represents the coordinates of each intersectionposition on the touch surface. Respective maximum values of i and j areM and N, as depicted in FIG. 1.

The multiplexer 13 is a circuit that plays a role of selecting theplurality of Y-electrodes 2 y one by one in order at predetermined timeintervals and connecting the selected Y-electrodes 2 y to an inputterminal of the analog to digital converter 14. The analog to digitalconverter 14 has a function of generating a digital signal by subjectingthe signal supplied from each Y-electrode 2 y to sampling andquantization and supplying the generated digital signal to the touchdetecting circuit 15.

When the finger F or the stylus P is in proximity to a certainintersection position (i, j), a capacitance occurs between anX-electrode 2 x and a Y-electrode 2 y in the vicinity of theintersection position (i, j) and the finger F or the stylus P, and thesignal is absorbed in the direction of a human body. As a result, theamplitude of the signal supplied from the Y-electrode 2 y to the analogto digital converter 14 is decreased, which is reflected in the value ofthe digital signal. The touch detecting circuit 15 is configured todetect a capacitance C (i, j) (first capacitance) between the finger For the stylus P and the touch sensor 2 for each intersection position(i, j) based on a change in the amplitude which change is thus reflectedin the value of the digital signal, and write the capacitance to a framememory FM in the storage device 20. Incidentally, as for a concreteconfiguration of the touch detecting circuit 15, the touch detectingcircuit 15 is suitably configured by a hardware circuit such, forexample, as a programmable logic controller. However, the touchdetecting circuit 15 may be configured by a processor that implementseach function to be described later by reading and executing a programstored in a memory not depicted.

By using a plurality of capacitances C written to the frame memory FM,the touch detecting circuit 15 detects the finger F or the stylus P andderives coordinates indicating the position of the detected finger F orthe detected stylus P on the touch surface. These pieces of processingwill be described in detail in the following.

FIG. 2 is a flowchart depicting processing performed by the touchdetecting circuit 15. The touch detecting circuit 15 is configured torepeat the processing depicted in the figure periodically.

As depicted in FIG. 2, the touch detecting circuit 15 first performsglobal labeling using a threshold value TH1 (first threshold value)(S1). The global labeling is processing of identifying an area (firstarea) on the touch surface in which area a plurality of capacitances Cexceed the threshold value TH1. The global labeling is performed todetermine the kind of a detected indicator.

FIG. 3A is a schematic diagram depicting a distribution of capacitancesC in a case where the finger F is present on the touch surface. FIG. 3Bis a schematic diagram depicting a distribution of capacitances C in acase where the stylus P is present on the touch surface. As isunderstood from comparison between these figures, in the case where thefinger F is present on the touch surface, a peak value of thecapacitances C is increased to a considerable degree as compared withthe case where the stylus P is present on the touch surface.Incidentally, the distribution of FIG. 3B has a shape such that a smallprotruding portion is disposed on a mountain portion having a largespread. Part of the mountain portion is attributable to noise (includingnoise caused by bending of the touch surface). Part of the protrudingportion corresponds to the position of the stylus P.

FIG. 7A is a diagram depicting a more concrete example of thecapacitances C detected in the case where the finger F is in contactwith the touch surface. FIG. 7B is a 3D contour map depicting adistribution of the capacitances C depicted in FIG. 7A. In addition,FIG. 8A is a diagram depicting a more concrete example of thecapacitances C detected in the case where the stylus P is in contactwith the touch surface. FIG. 8B is a 3D contour map depicting adistribution of the capacitances C depicted in FIG. 8A. It is understoodalso from these figures that in the case where the finger F is presenton the touch surface, the peak value of the capacitances C is increasedto a considerable degree as compared with the case where the stylus P ispresent on the touch surface. In addition, as is understood by referringalso to FIGS. 9A and 9B and FIGS. 10A and 10B to be described later, thedistribution of FIGS. 8A and 8B is such that a small protruding portionis disposed on a mountain having a spread.

The description returns to FIG. 3. The threshold value TH1 is set to avalue normally expected to be positioned between an upper end and alower end of the above-described protruding portion. When the thresholdvalue TH1 is set to such a value, as is understood from FIG. 3A and FIG.3B, the size of an area in which capacitances C exceed the thresholdvalue TH1 is relatively large in the case where the finger F is presenton the touch surface (illustrated area GLF), and the size of the area isrelatively small in the case where the stylus P is present on the touchsurface (illustrated area GLP). Hence, the touch detecting circuit 15can determine the kind of the detected indicator by calculating the sizeof the area on the touch surface in which area a plurality ofcapacitances C exceed the threshold value TH1.

The description returns to FIG. 2. After performing S1, the touchdetecting circuit 15 determines the kind of the detected indicator basedon the area (the area GLF or the area GLP) identified by the globallabeling (S2). When the touch detecting circuit 15 identifies the fingerF at S2, the touch detecting circuit 15 derives a threshold value TH_F(third threshold value) for the detection of the finger F from a maximumvalue of the detected capacitances (S3).

The derivation of the threshold value THF will be described withreference to FIG. 3A again. As depicted in the figure, the touchdetecting circuit 15 derives the threshold value TH_F=MAX-D_F bysubtracting a predetermined value D_F (second value) from a maximumvalue MAX of the detected capacitances. The value of the predeterminedvalue D_F is determined in advance such that the threshold value TH_F isa value larger than the threshold value TH1.

The description returns to FIG. 2. The touch detecting circuit 15performs local labeling using the derived threshold value TH_F (S4). Thelocal labeling in this case is processing of identifying an area (thirdarea) on the touch surface in which area capacitances C exceed thethreshold value TH_F. An area LLF depicted in FIG. 3A is an example ofthe thus identified third area. Next, the touch detecting circuit 15derives coordinates indicating the position of the finger F based on aresult of the local labeling (S5). In a concrete example, the touchdetecting circuit 15 derives the center of gravity of the third area asthe coordinates indicating the position of the finger F. The touchdetecting circuit 15 outputs the derived coordinates indicating theposition of the finger F to the host CPU (see FIG. 2). The touchdetecting circuit 15 then ends the processing.

When the touch detecting circuit 15 identifies the stylus P at S2, thetouch detecting circuit 15 first performs processing of reducing noiseincluded in the plurality of capacitances C by processing the detectedplurality of capacitances by a predetermined second filter (S6). Thesecond filter is, specifically, a Gaussian filter that smooths theplurality of capacitances C.

FIG. 4 is a diagram depicting an example of the Gaussian filter used atS6. The Gaussian filter according to the present example is a matrix ofthree rows and three columns. The touch detecting circuit 15 obtainscapacitances C1 (i, j) after processing by the Gaussian filter accordingto the following Equation (1). In Equation (1), m and n are each aninteger of 1 to 3, and G (m, n) denotes an element in an mth row and annth column of the Gaussian filter.

$\begin{matrix}{\lbrack {{Equation}\mspace{14mu} 1} \rbrack\mspace{619mu}} & \; \\{{C\; 1( {i,j} )} = {\sum\limits_{m,{n = 1}}^{3}{\frac{G( {m,n} )}{\sum_{m,{n = 1}}^{3}{G( {m,n} )}} \times {C( {{i + m - 2},{j + n - 2}} )}}}} & (1)\end{matrix}$

FIG. 6A is a schematic diagram depicting the capacitances C1 obtained byprocessing the capacitances C depicted in FIG. 3B by the Gaussian filterdepicted in FIG. 4. As is understood from comparison between FIG. 6A andFIG. 3B, the capacitances C1 are reduced in noise as compared with thecapacitances C as a result of the processing by the Gaussian filter.

FIG. 9A is a diagram depicting the capacitances C1 obtained byprocessing the capacitances C depicted in FIG. 8A by the Gaussian filterof FIG. 4. FIG. 9B is a 3D contour map depicting a distribution of thecapacitances C1 depicted in FIG. 9A. It is understood also fromcomparison between FIGS. 9A and 9B and FIGS. 8A and 8B that noise can beremoved from the capacitances C by processing the capacitances C by theGaussian filter.

The description returns to FIG. 2. After performing S6, the touchdetecting circuit 15 next performs processing of emphasizing a peakincluded in the plurality of capacitances C1 by processing the detectedplurality of capacitances C1 by a predetermined first filter (S7). Thefirst filter is, specifically, a high-pass filter that emphasizeschanges in the capacitances C1 on the touch surface.

FIGS. 5A and 5B are each a diagram depicting an example of the high-passfilter used at S7. Incidentally, a sequence (0, 9, 0) in a verticaldirection and a sequence (−2, 9, −2) in a horizontal direction in thehigh-pass filter depicted in FIG. 5B are different from each other inorder to reduce an effect of the bending of the touch surface. Thehigh-pass filters according to these examples are a matrix of three rowsand three columns. The touch detecting circuit 15 obtains capacitancesC2 (i, j) (second capacitance) after processing by the high-pass filteraccording to the following Equation (2). However, in Equation (2), m andn are each an integer of 1 to 3, and H (m, n) denotes each element ofthe high-pass filter.

$\begin{matrix}{\lbrack {{Equation}\mspace{14mu} 2} \rbrack\mspace{619mu}} & \; \\{{C\; 2( {i,j} )} = {\sum\limits_{m,{n = 1}}^{3}{{H( {m,n} )} \times C\; 1( {{i + m - 2},{j + n - 2}} )}}} & (2)\end{matrix}$

FIG. 6B is a schematic diagram depicting the capacitances C2 obtained byprocessing the capacitances C1 depicted in FIG. 6A by the high-passfilter depicted in FIG. 5A or FIG. 5B. As is understood from comparisonof FIG. 6B with FIG. 3B and FIG. 6A, a peak of the capacitances C2 isemphasized as a result of the processing by the high-pass filter ascompared with the capacitances C and C1.

FIG. 10A is a diagram depicting the capacitances C2 obtained byprocessing the capacitances C1 depicted in FIG. 9A by the high-passfilter of FIG. 5B. FIG. 10B is a 3D contour map depicting a distributionof the capacitances C2 depicted in FIG. 10A. It is understood also fromcomparison of FIGS. 10A and 10B with FIGS. 9A and 9B that a peakincluded in the capacitances C1 can be emphasized by processing thecapacitances C1 by the high-pass filter.

The description returns to FIG. 2. After performing S6 and S7, the touchdetecting circuit 15 next derives a threshold value TH_P (secondthreshold value) for the detection of the stylus P from a maximum valueof the capacitances C2 (S8).

The derivation of the threshold value TH_P will be described withreference to FIG. 6B again. As depicted in the figure, the touchdetecting circuit 15 derives a threshold value TH_P=MAX-D_P bysubtracting a predetermined value D_P (first value) from a maximum valueMAX of the detected capacitances C2. The value of the predeterminedvalue D_P is determined in advance such that the threshold value TH_P isa value larger than the threshold value TH1. Incidentally, thepredetermined value D_P can be set to be a value equal to thepredetermined value D_F described above.

The description returns to FIG. 2. The touch detecting circuit 15performs local labeling using the derived threshold value TH_P (S9). Thelocal labeling in this case is processing of identifying an area (secondarea) on the touch surface in which area capacitances C2 exceed thethreshold value TH_P. An area LLP depicted in FIG. 6B is an example ofthe thus identified second area. Next, the touch detecting circuit 15derives coordinates indicating the position of the stylus P based on aresult of the local labeling (S10). In a concrete example, the touchdetecting circuit 15 derives the center of gravity of the second area asthe coordinates indicating the position of the stylus P. The touchdetecting circuit 15 outputs the derived coordinates indicating theposition of the stylus P to the host CPU (see FIG. 2). The touchdetecting circuit 15 then ends the processing.

As described above, according to the touch detecting method and thetouch detecting device 1 in accordance with the present embodiment, thefinger F is detected using the third threshold value larger than thefirst threshold value. Thus, the detection of the finger F can beperformed suitably. In addition, the stylus P is detected using thesecond threshold value larger than the first threshold value after thepeak is emphasized by a filter. Thus, the detection of the stylus P canalso be performed suitably. Hence, according to the touch detectingmethod and the touch detecting device 1 in accordance with the presentembodiment, the detection of the finger F and the stylus P can beperformed suitably.

The preferred embodiment of the present disclosure has been describedabove. However, the present disclosure is not at all limited to suchembodiment, but the present disclosure can of course be carried out invarious modes without departing from the spirit of the presentdisclosure.

For example, as described in Japanese Patent No. 5901870, the touchdetecting circuit 15 may write, to the frame memory FM, a value formedby subtracting a reference value for each intersection position (i, j)from the capacitance C (i, j) in place of the capacitance C (i, j).Then, as described in the foregoing embodiment, this value written tothe frame memory FM may be used to detect the finger F or the stylus Pand derive the coordinates indicating the position of the detectedfinger F or the detected stylus P on the touch surface. It is therebypossible to reduce an effect of bending caused by depression of thetouch surface.

In addition, while filters as matrices of three rows and three columnsare depicted in FIG. 4 and FIGS. 5A and 5B, other kinds of filters canalso be used. Further, while FIG. 2 depicts an example in which theGaussian filter and the high-pass filter are applied in this order, thehigh-pass filter may be applied first. Besides, noise reduction by theGaussian filter may be omitted.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A touch detecting method performed by a touch detecting deviceconnected to a touch sensor constituting a touch surface, the touchdetecting method comprising: determining a kind of a detected indicatorbased on a first area on the touch surface, the first area being an areain which each of a plurality of first capacitances corresponding to aplurality of coordinates on the touch surface exceeds a first thresholdvalue; obtaining a plurality of second capacitances formed byemphasizing a peak in comparison with the plurality of firstcapacitances by processing the plurality of first capacitances by afirst filter in a case where the determining determines that thedetected indicator is a stylus; deriving coordinates indicating aposition of the stylus on the touch surface based on a second area onthe touch surface, the second area being an area in which each of theplurality of second capacitances exceeds a second threshold value thatis larger than the first threshold value; and deriving coordinatesindicating a position of a finger on the touch surface based on a thirdarea on the touch surface, the third area being an area in which each ofthe plurality of first capacitances exceeds a third threshold valuelarger than the first threshold value, in a case where the determiningdetermines that the detected indicator is the finger.
 2. The touchdetecting method according to claim 1, further comprising: deriving thesecond threshold value by subtracting a predetermined first value from amaximum value of the plurality of second capacitances within the firstarea.
 3. The touch detecting method according to claim 2, furthercomprising: deriving the third threshold value by subtracting apredetermined second value from a maximum value of the plurality offirst capacitances within the first area.
 4. The touch detecting methodaccording to claim 3, wherein the first value and the second value areequal to each other.
 5. The touch detecting method according to claim 1,wherein the obtaining the plurality of second capacitances includesobtaining the plurality of second capacitances formed by emphasizing thepeak in comparison with the plurality of first capacitances and reducingnoise in comparison with the plurality of first capacitances, byprocessing the plurality of first capacitances by each of the firstfilter and a second filter.
 6. The touch detecting method according toclaim 5, wherein: the obtaining the plurality of second capacitancesincludes processing the plurality of first capacitances by the firstfilter, and processing, by the second filter, the plurality of firstcapacitances after being processed by the first filter, the first filteris a high-pass filter that emphasizes changes in the plurality of firstcapacitances on the touch surface, and the second filter is a Gaussianfilter that smooths the plurality of first capacitances after beingprocessed by the first filter.
 7. The touch detecting method accordingto claim 5, wherein: the obtaining the plurality of second capacitancesincludes processing, by the second filter, the plurality of firstcapacitances, and processing, by the first filter, the plurality offirst capacitances after being processed by the second filter, thesecond filter is a Gaussian filter that smooths the plurality of firstcapacitances, and the first filter is a high-pass filter that emphasizeschanges in the plurality of first capacitances after being processed bythe second filter within the touch surface.
 8. A touch detecting deviceconnected to a touch sensor constituting a touch surface, the touchdetecting device comprising: an analog to digital converter which, inoperation, generates a digital signal based on an analog signal receivedfrom the touch sensor; and a touch detecting circuit coupled to theanalog to digital converter, wherein the touch detecting circuit, inoperation, determines a kind of a detected indicator based on a firstarea on the touch surface, the first area being an area in which each ofa plurality of first capacitances corresponding to a plurality ofcoordinates on the touch surface exceeds a first threshold value;obtains a plurality of second capacitances formed by emphasizing a peakin comparison with the plurality of first capacitances by processing theplurality of first capacitances by a first filter in a case where thedetected indicator is determined to be a stylus; derives coordinatesindicating a position of the stylus on the touch surface based on asecond area on the touch surface, the second area being an area in whicheach of the plurality of second capacitances exceeds a second thresholdvalue larger than the first threshold value; and derives coordinatesindicating a position of a finger on the touch surface based on a thirdarea on the touch surface, the third area being an area in which each ofthe plurality of first capacitances exceeds a third threshold valuelarger than the first threshold value, in a case where the detectedindicator is determined to be the finger.
 9. The touch detecting deviceaccording to claim 8, wherein the touch detecting circuit, in operation,derives the second threshold value by subtracting a predetermined firstvalue from a maximum value of the plurality of second capacitanceswithin the first area.
 10. The touch detecting device according to claim9, wherein the touch detecting circuit, in operation, derives the thirdthreshold value by subtracting a predetermined second value from amaximum value of the plurality of first capacitances within the firstarea.
 11. The touch detecting device according to claim 10, wherein thefirst value and the second value are equal to each other.
 12. The touchdetecting device according to claim 8, wherein the touch detectingcircuit, in operation, obtains the plurality of second capacitances byobtaining the plurality of second capacitances formed by emphasizing thepeak in comparison with the plurality of first capacitances and reducingnoise in comparison with the plurality of first capacitances, byprocessing the plurality of first capacitances by each of the firstfilter and a second filter.
 13. The touch detecting device according toclaim 12, wherein: the touch detecting circuit, in operation, obtainsthe plurality of second capacitances by processing, by the first filter,the plurality of first capacitances, and processing, by the secondfilter, the plurality of first capacitances after being processed by thefirst filter, the first filter is a high-pass filter that emphasizeschanges in the plurality of first capacitances on the touch surface, andthe second filter is a Gaussian filter that smooths the plurality offirst capacitances after being processed by the first filter.
 14. Thetouch detecting device according to claim 12, wherein: the touchdetecting circuit, in operation, obtains the plurality of secondcapacitances by processing the plurality of first capacitances by thesecond filter, and processing, by the first filter, the plurality offirst capacitances after being processed by the second filter, thesecond filter is a Gaussian filter that smooths the plurality of firstcapacitances, and the first filter is a high-pass filter that emphasizeschanges in the plurality of first capacitances after being processed bythe second filter within the touch surface.